1. Field
A linear compressor is disclosed herein.
2. Background
Generally, a compressor is a mechanical device that increases pressure by compressing air, refrigerant, or a variety of working gases, with power received from a power generating apparatus, such as an electric motor or a turbine. The linear compressor is widely used in home appliances, such as refrigerators or air conditioners, and is also used for various industrial purposes.
The compressor can be categorized mainly into a reciprocating compressor, in which a compression space is defined between a piston and a cylinder, into and from which a working gas, such as a refrigerant, is suctioned and discharged, such that the piston is linearly reciprocated in an interior of the cylinder to compress the refrigerant; a rotary compressor, in which a compression space is defined between an eccentrically-rotating roller and a cylinder, into and from which a working gas, such as a refrigerant, is suctioned and discharged, so that the roller is eccentrically rotated along an inner wall of the cylinder to compress the refrigerant; or a scroll compressor, in which a compression space is defined between an orbiting scroll and a fixed scroll, into and from which a working gas, such as a refrigerant, is suctioned and discharged, so that the orbiting scroll is rotated along the fixed scroll to compress the refrigerant. Among recent reciprocating compressors, linear compressors have been particularly developed, because the linear compressors have a construction in which the piston is directly connected to a linearly-reciprocating drive motor, thus providing improved compression efficiency without suffering mechanical loss due to transformation of motions. The linear compressor may be generally constructed so that the piston in a sealed shell is linearly reciprocated within the cylinder by the linear motor, to draw in refrigerant, compress, and discharge the same.
The linear motor may be so configured that a permanent magnet is positioned between an inner stator and an outer stator, and may be linearly reciprocated by an electromagnetic force between the permanent magnet and the inner (or outer) stator. Accordingly, as the permanent magnet connected with the piston is driven, the piston is linearly reciprocated within the cylinder, thus drawing in refrigerant, compressing, and discharging the same.
FIGS. 1 and 2 are schematic cross-sectional views of a related linear compressor 1. The related art linear compressor 1 of FIGS. 1-2 may include a cylinder 6, a piston 7, which may be linearly reciprocated within the cylinder 6, and a linear motor that provides the piston 7 with a drive force. The cylinder 6 may be fixed by a frame 5. The frame 5 may be integrally formed with the cylinder 6 or fastened thereto by a separate fastening member, for example.
The linear motor may include an outer stator 2 fixed to the frame 5 and arranged to surround the cylinder 6, an inner stator 3 spaced from an inner side of the outer stator 2, and a permanent magnet 10 disposed in a space between the outer stator 2 and the inner stator 3. The outer stator 2 may include a coil 4.
The linear compressor 1 may additionally include a magnet frame 11. The magnet frame 11 may transmit the drive force of the linear motor to the piston 7. The permanent magnet 10 may be mounted on an outer circumference of the magnet frame 11. The linear compressor 1 may additionally include a supporter 8 that supports the piston 7, and a motor cover 9 engaged to a side of the outer stator 2.
A spring (not illustrated) may be engaged between the supporter 8 and the motor cover 9. The spring may have a natural frequency so adjusted to allow the piston 7 to resonate.
The linear compressor 1 may further include a muffler 12 that extends from an interior of the piston 7 to the outside. The muffler 12 may deaden noise generated by refrigerant flow.
With the above-described construction, when the linear motor is driven, the drive assembly, that is, the magnet frame 11, the permanent magnet 10, the piston 7, and the supporter 8 may be integrally reciprocated.
FIG. 1 illustrates the piston 7 at a bottom dead center (BDC) position, at which the refrigerant is not compressed, while FIG. 2 illustrates the piston 7 at a top dead center (TDC) position, at which the refrigerant is compressed. The piston 7 may linearly reciprocate between the BDC and TDC positions.
The reciprocating motion of the drive assembly (7, 8, 10, 11) may be performed under electric control of the linear motor or structural elastic control of the spring. The drive assembly may be controlled so as not to interfere with stationary components in the linear compressor 1, such as, for example, the frame 5, the cylinder 6, or the motor cover 9, during reciprocating motion.
During driving of the linear compressor, an emergency may occur where the drive assembly is out of control or partially not controllable. In such a situation, the drive assembly and stationary components may interfere or even collide against each other.
Accordingly, to ensure reliability of the compressor, the compressor may be so designed that the drive assembly or the stationary components are brought into contact or collision at locations that are less subject to breakage. The locations that are less subject to breakage may be portions of the drive assembly that have relatively greater mass. As an inertial force of a reciprocating object is in proportion to a mass of the object, this means that the possibility of breakage is lower when a colliding portion of the reciprocating object has a relatively greater mass, because the resting portion has a relatively smaller mass, and thus, has less inertial force.
On the other hand, the possibility of breakage increases when the colliding portion of the reciprocating object has a relatively smaller mass, because the resting portion has a relatively greater mass, and thus, has a greater inertial force. Accordingly, the drive assembly may be designed so that the portion with relatively greater mass collides when an emergency occurs.
In the linear compressor 1 according to the related art, a rare earth magnet, for example, a neodymium magnet or ND magnet, may be used as the permanent magnet 10. Although the ND magnet has a relatively high magnetic flux density, due to expensive cost, only a small amount of the magnet is used. Therefore, the permanent magnet 10 is formed to have a low mass.
In contrast, the piston 7 or the supporter 8 has a relatively greater mass among the drive assembly. Accordingly, the related art linear compressor 1 is so designed that when collision has to occur during reciprocating motion of the drive assembly, the piston 7 and the cylinder 6, or the supporter 8 and the motor cover 9 are the first ones to collide.
For example, referring to FIG. 2, when the piston 7 is located at the TDC position, the piston 7 may contact or collide against an end of the cylinder 6, in which case the permanent magnet 10 may be prevented from contacting or colliding with the frame 5 (see “C”).
Although not illustrated, in another example, the piston 7 may be at the TDC position, in which case at least a portion of the supporter 8 may be brought into contact with or collide against the motor cover 9, while the permanent magnet 10 may be prevented from contacting or colliding with the frame 5.
According to the related art technologies discussed above, when the ND magnet is used as the permanent magnet, the expensive price of the ND magnet may increase manufacture costs of the linear compressor. Additionally, due to the considerable size of magnetic flux leaking from the ND magnet, operating efficiency of the compressor may deteriorate.